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i  iMiVERSITY  OF  ILLINOIS, 


UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station. 


URBANA,  AUGUST,  1903. 


BULLETIN   No.  87. 


THE  STRUCTURE  OF  THE  CORN  KERNEL 

AND  THE  COMPOSITION  OF  ITS 

DIFFERENT  PARTS. 


BY  CYRIL  G.  HOPKINS,  PH.  D.,  CHIEF  IN  AGRONOMY  AND  CHEMISTRY; 
LOUIE  H.  SMITH,  M.  S.,  CHIEF  ASSISTANT  IN  CHEMISTRY  AND  PLANT 
BREEDING;  AND  EDWARD  M.  EAST,  B.  S.,  ASSISTANT  IN  CHEMISTRY. 


The  possibility  of  selecting  seed  corn  for  improved  chemical  composi- 
tion by  a  simple  mechanical  examination  of  sections  of  kernels  (which 
any  one  can  easily  make  with  a  pocket-knife)  was  clearly  established  by 
the  experiments  reported  in  Bulletin  No.  55,  "  Improvement  in  the 
Chemical  Composition  of  the  Corn  Kernel" ;  and  the  practical  value  of 
this  method  of  selecting  seed  corn  for  high  protein,  high  oil,  or  other  de- 
sirable qualities  has  been  fully  confirmed  by  subsequent  investigations 
and  trials  by  the  Experiment  Station  and  by  practical  seed-corn  breeders, 
as  shown  in  Bulletin  No.  82,  "  Methods  of  Corn  Breeding." 

77 


78 


BULLETIN  No.  87. 


[August, 


A  considerable  amount  of  additional  data  relating  to  this  matter  has 
been  accumulating  with  the  progress  of  our  experiments  in  corn  breed- 
ing, and  because  of  the  very  great  importance  of  this  subject  to  the 
corn  growers  and  corn  breeders  of  Illinois,  and  also  because  of  the  marked 


Stem  J 

Embryo) 
Boot    j 


PLATE  1.— LOW-PROTEIN  CORN  KERNEL  FROM  DRAWING  (SMALL  KERNELS 
FROM  PHOTOURAPH). 


1903.] 


THE  STRUCTURE  OP  THE  CORN  KERNEL. 


79 


interest  which  is  manifested  in  this  matter  both  by  progressive,  prac- 
tical farmers  and  by  scientific  investigators,  it  has  seemed  advisable  to 
publish  in  somewhat  greater  detail  the  results  of  our  investigations  along 
this  line. 


Horny 
Gluten 


Horny 
[Starch 


HmbryoL 

Stem  J 

Embryo 


Boob 


Tip 
Starch 

[Tip 

[Cap 


PLATE  2. — HIGH-PROTEIN  CORN  KERNEL  FROM  DRAWING  (SMALL  KERNELS 
FROM  PHOTOGRAPH). 


10  BULLETIN  No.  87.  [August, 

PARTS  OF  THE  CORN  KERNEL. 

There  are  six  distinctly  different  parts  in  a  kernel  of  corn,  as  will  be 
readily  seen  by  reference  to  Plates  1  and  2. 

1.  TIP  CAP. — This  is  a  small  cap  covering  the  tip  end  of  the  kernel 
and  serves  as  a  protection  to  the  end  of  the  germ.     It  consists  of  material 
somewhat  resembling  the  cob  and  occasionally  in  shelling  corn  the  tip 
cap  remains  attached  to  the  cob,  leaving  the  tip  end  of  the  germ  un- 
covered, but  nearly  always  it  remains  on  the  kernel. 

2.  HULL. — This  is  the  very  thin  outer  covering  of  the  kernel.  It  con- 
sists largely  of  carbohydrates,  especially  fiber  or  cellulose,  although  it 
also  contains  a  small  percentage  of  other  constituents. 

3.  HORNY  GLUTENOUS  PART. — This  part  lies  immediately  underneath 
the  hull.     It  constitutes  a  second  covering  of  the  kernel,  usually  much 
thicker  than  the  hull.     For  short,  it  is  called  horny  gluten,  although  it 
is,  of  course,  not  pure  gluten.     However,  it  is  the  richest  in  protein  of 
any  part  of  the  corn  kernel,  as  has  been  stated  in  bulletins  already  pub- 
lished by  this  station  and  previously  by  Doctor  Voorhees,  Director  of  the 
New  Jersey  Experiment  Station. 

4.  HORNY  STARCHY  PART. — This  part  lies  next  to  the  horny  gluten, 
on  the  back  and  sides  of  the  kernel.    For  short,  it  is  called  homy  starch, 
although  it  is  not  pure  starch,  as  it  contains  considerable  amounts  of 
other  constituents,  especially  of  protein.     In  an  examination  of  the 
kernel  with  the  unaided  eye  the  horny  glutenous  part  and  the  horny 
starchy  part  are  not  readily  distinguished  from  each  other,  the  line  be- 
tween them  being  somewhat  indefinite  and  indistinct.     Considered  both 
together  these  two  parts  constitute  the  horny  part  of  the  kernel. 

5.  WHITE  STARCHY  PART. — This  part  occupies  the  crown  end  of  the 
kernel  above  the  germ  and  it  also  nearly  surrounds  the  germ  toward  the 
tip  end  of  the  kernel.     For  convenience  this  material  is  called  white 
starch,  although  it  is  not  pure  starch  as  has  been  clearly  shown  in  former 
publications.     In  some  kernels  the  horny  starch  extends  nearly  or  quite 
to  the  germ  (near  the  middle  of  the  kernel)  and  thus  separates  more  or 
less  completely  the  white  starch  into  two  parts  which  we  call  crown 
starch  and  tip  starch. 

6.  GERM. — The  germ  occupies  the  center  of  the  front  of  the  kernel 
toward  the  tip  end  and  usually  extends  about  one-half  or  two-thirds  of 
the  length  of  the  kernel.     Within  the  body  of  the  germ  are  the  embryo 
stem  pointing  upward  toward  the  crown  end  and  the  embryo  root  point- 
ing downward  toward  the  tip  of  the  kernel,  both  of  which  are,  of  course, 
parts  of  the  germ.     These  embryo  parts  within  the  germ  may  be  easily 
seen  by  any  one  who  will  carefully  shave  off  the  front  side  of  the  germ 
from  a  kernel  of  corn.     (See  small  photographic  reproduction  of  sections 
of  kernels  of  high  and  low  protein  corn  in  Plates  1  and  2.) 


1903.]  THE  STRUCTURE  OF  THE  CORN  KERNEL.  81 

MECHANICAL  SEPARATION  OF  THE  DIFFERENT  PARTS. 

It  is  not  a  difficult  matter  to  obtain  very  pure  samples  of  each  of  the 
above-named  parts  of  the  corn  kernel,  although  in  making  the  separa- 
tions there  is  of  necessity  some  waste  material  consisting  of  a  mixture  of 
three  different  parts:  namely,  horny  gluten,  horny  starch,  and  white 
starch. 

By  the  use  of  a  small  sharp  knife  any  one  can  make  the  following 
separations : 

1.  Tip  cap. 

2.  Hull. 

3.  Horny  gluten. 

4.  Horny  starch.* 
5a.  Crown  starch. 
5b.  Tip  starch. 

6.  Germ. 

7.  Waste  (mixed  material). 

In  making  these  separations  the  kernels  are  first  soaked  in  hot  water 
for  fifteen  or  twenty  minutes. 

The  tip  cap  is  then  very  easily  and  perfectly  separated  by  simply 
cutting  under  one  edge  and  then  pulling  it  off. 

The  hull  is  separated  without  difficulty  by  peeling  it  off  in  strips.  It 
is  only  necessary  to  use  the  knife  to  start  the  peeling  at  the  tip  end  where 
the  hull  has  been  broken  by  removing  the  tip  cap.  With  some  care  the 
hull  can  be  completely  peeled  out  of  the  dent  in  the  corn. 

The  horny  gluten  is  more  easily  distinguished  after  the  hull  is  re- 
moved. It  will  be  plainly  seen  that  it  covers  the  entire  kernel,  except- 
ing possibly  the  exposed  part  of  the  germ.  The  horny  gluten  is  removed 
by  carefully  shaving  it  off  with  a  sharp  knife.  Adhering  particles  of 
starch  can  be  more  easily  separated  from  the  horny  gluten  after  the 
shavings  have  been  allowed  to  dry  for  some  time.  In  scraping  off  these 
particles  of  horny  starch  or  white  starch  adhering  to  the  shavings,  more 
or  less  horny  gluten  will  also  be  scraped  off,  so  that,  while  we  are  thus 
able  to  obtain  a  pure  clean  sample  of  the  horny  gluten,  we  also  obtain 
some  waste  material,  consisting  of  particles  of  horny  gluten,  horny  starch, 
and  white  starch. 

The  germ  is  next  removed,  and  with  care  this  can  be  done  very  per- 
fectly. If  any  particles  of  starch  adhere  to  the  germ  they  can  easily  be 
completely  removed.  After  the  tip  cap,  hull,  horny  gluten,  and  germ 
have  been  removed,  the  remainder  of  the  kernel,  consisting  of  the  horny 
starch  and  white  starch  only,  is  allowed  to  dry,  and  the  kernel  is  broken 
in  two  lengthwise. 


*As  used  in  this  bulletin  the  term  "starch"  is  employed  in  a  technical  or  com- 
mercial sense,  and  not  as  the  name  of  a  definite  chemical  compound. 


82  BULLETIN  No.  87.  [August, 

The  crown  starch  is  dug  out  with  the  knife  as  completely  as  possible 
without  taking  any  of  the  horny  starch. 

The  tip  starch  is  next  removed  in  the  same  manner  as  the  crown  starch. 

The  horny  starch  from  each  side  usually  remains  in  a  solid  piece. 
This  is  now  carefully  scraped  to  remove  all  adhering  particles  of  white 
starch  or  horny  gluten,  the  scrapings  being  carefully  saved  and  added  to 
the  waste  material. 

By  this  method  of  separation  we  obtain  eight  different  products,  in- 
cluding the  waste  material,  and  seven  of  these  products  are  pure  samples 
of  distinctly  different  parts  of  the  corn  kernel,  excepting  the  crown  starch 
and  tip  starch,  both  of  which,  of  course,  belong  to  the  white  starch;  they 
are  kept  separate,  however,  because  they  are  found  in  different  places, 
frequently  being  entirely  separated  in  the  kernel,  although  more  com- 
monly there  is  some  white  starch  continuous  from  crown  to  tip. 

COMPOSITION  OF  THE  DIFFERENT  PARTS. 

Table  1  shows  the  percentage  of  these  eight  different  products,  or 
parts,  and  the  percentage  composition  of  each  part,  also  the  percentage 
composition  of  the  whole  corn,  for  each  of  three  different  ears  of  corn. 
Ear  No.  1  is  corn  of  comparatively  low*  protein  content  (see  foot-note). 
Ear  No.  2  has  about  the  usual  protein  content  of  ordinary  corn.  Ear 
No.  3  is  high*  protein  corn  (see  foot-note).  About  200  grams  (nearly 
one-half  pound)  of  kernels  from  each  ear  were  separated  into  the  differ- 
ent parts,  and  each  part  was  then  weighed  and  analyzed  separately, 
another  sample  of  the  corn  from  each  ear  being  analyzed  to  give  the  com- 
position of  the  whole  corn.  (All  results  are  given  on  the  water-free  basis.) 


*It  should  be  understood  that  Ear  No.  1  (9.28  percent  protein)  and  Ear  No.  3 
(12.85  percent  protein)  do  not  represent  extremes  in  protein  content;  indeed,  in 
our  breeding  of  corn  for  low  protein  we  have  produced  good  ears  containing  less 
than  6.50  percent  of  protein,  and  in  our  high  protein  field  we  have  produced  corn 
containing  over  16  percent  of  protein.  In  extremely  low  protein  corn  the  per- 
centage of  horny  part  is  very  much  less  than  in  Ear  No.  1,  and  in  extremely  high 
protein  corn  the  tip  white  starch  is  frequently  almost  entirely  wanting  and  the  crown 
white  starch  very  greatly  reduced,  both  being  replaced  by  the  horny  part,  as  shown 
in  the  drawings  and  also  in  the  actual  photographs  of  sections  of  kernels  shown 
beside  the  drawings  in  Plates  1  and  2. 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


83 


TABLE  1. — PERCENTAGE  OF  DIFFERENT  PARTS  AND  PERCENTAGE  COMPOSITION  OF 

EACH  PART. 


Ear  No.  1  (low  in  protein). 


Names  of  parts. 

Percent 
of 
whole. 

.Composition  of  parts. 

Protein, 
percent. 

Oil, 
percent. 

Ash, 
percent. 

Carbo- 
hydrates, 
percent. 

Tip  caps    . 

1.20 
5.47 

7.75 
29.58 

16.94 
10.93 

9.59 
18.53 

7.36 
4.97 

19.21 
8.12 

7.22 
6.10 

19.91 
9.90 

9.28 

1.16 
.92 

4.00 
.16 

.19 
.29 

36.54 
1.06 

4.20 

.91 

.82 

.92 
.18 

.32 
.29 

10.48 
.61 

1.41 

90.57 
93.29 

75.87 
91.54 

92.27 
93.31 

33  .07 

88.43 

85.11 

Hulls  

Horny  gluten  

Hornv  starch  .            .  . 

Crown  starch    

Tip  starch  

Germs  

Mixed  waste  

Whole  corn.  . 

Ear  No.  2  (medium  in  protein). 


Tip  caps  

1.46 

8.83 

2.30 

1.11 

87.76 

Hulls  . 

5  93 

3  96 

89 

79 

94  36 

Horny  gluten  . 

5  12 

22  50 

6  99 

1  72 

69  09 

Horny  starch  . 

32  80 

10  20 

24 

24 

89  32 

Crown  starch    

11  85 

7  92 

17 

.24 

91.67 

Tip  starch   

5  91 

7  68 

39 

.31 

91.62 

Germs  

11.53 

19.80 

34.84 

9.90 

35.46 

Mixed  waste.. 

25  40 

11  10 

1  23 

57 

87.10 

Whole  corn.  . 

10.95 

4.33 

1.55 

83.17 

Ear  No.  3  (high  in  protein). 


Tip  caps  

1.62 

4.64 

1.99 

1.87 

91.50 

Hulls  .                    .... 

6  09 

3  84 

76 

1.10 

94.30 

Horny  gluten  

9.86 

24.58 

4.61 

1.74 

69.07 

Horny  starch  

33.79 

10.99 

.22 

.21 

88.58 

Crown  starch  

10  45 

8.61 

.52 

.37 

90.50 

Tip  starch  

6.23 

7.29 

1.36 

.60 

90.75 

Germs  

11  93 

19.56 

33.71 

10.00 

36.73 

Mixed  waste  

20  03 

12.53 

1.15 

.61 

85.71 

Whole  corn.  . 

12.85 

5.36 

1.67 

80.12 

A  careful  study  of  Table  1  reveals  some  very  interesting  and  useful 
facts  regarding  the  structure  of  the  corn  kernel  and  the  composition  of 
the  different  parts.  It  is  certainly  an  interesting  fact  that  there  are  so 


84  BULLETIN  No.  87.  [August, 

many  different  parts  in  a  kernel  of  corn,  and  it  is  exceedingly  useful  to  be 
able  by  a  mechanical  examination  of  corn  not  only  to  pick  out  high  pro- 
tein corn  or  high  oil  corn  as  one  may  desire,  but  even  to  separate  the 
several  distinctly  different  parts  from  one  another  by  purely  mechanical 
means — to  separate,  for  example,  the  horny  gluten,  containing  (in  the 
high  protein  ear)  nearly  25  •  percent  of  protein,  and  then  the  white 
starchy  parts,  with  only  7  or  8  percent  of  protein ;  or  the  germs  containing 
about  35  percent  of  oil  and  10  percent  of  ash,  and  then  the  horny 
starchy  part  containing  less  than  0.25  percent  of  either  oil  or  ash. 

The  hulls  contain  about  4  percent  of  protein  and  are  clearly  the  poorest 
in  protein  of  any  part  of  the  kernel,  the  next  poorest  being  the  tip  caps 
and  white  starchy  parts,  containing  about  7  or  8  percent,  the  tip  starch 
being  slightly  poorer  than  the  crown  starch.  The  horny  starch  is  richer 
in  protein  than  the  white  starch,  especially  in  the  medium  and  high  pro- 
tein corn  where  the  difference  amounts  to  more  than  2  percent,  the 
horny  starchy  part  containing  from  10  to  11  percent  of  protein.  The 
protein  content  of  the  germs  is  very  uniform  in  the  different  ears,  although 
the  poorest  germs  are  found  in  the  high  protein  corn,  and  the  richest  in 
the  low  protein  corn,  the  variation  being  from  19.56  to  19.91  percent. 
The  horny  gluten  is  the  richest  in  protein  of  any  part  of  the  kernel  in  both 
ordinary  and  high  protein  corn,  as  was  pointed  out  several  years  ago  by 
Doctor  Voorhees,*  Director  of  the  New  Jersey  Experiment  Station,  and 
as  we  have  quoted  in  previous  publications  of  the  Illinois  Experiment 
Station.  In  the  high  protein  corn  the  protein  content  of  the  horny 
gluten  amounts  to  24.58  percent.  In  the  low  protein  corn  it  is  slightly 
less  than  that  of  the  germ. 

It  is  plainly  seen  that  the  oil  in  corn  is  very  largely  in  the  germ,  al- 
though the  horny  gluten  also  contains  a  considerable  percentage,  the  germ 
containing  about  35  percent  of  oil  and  the  horny  gluten  about  5  per- 
cent. Both  the  horny  starch  and  white  starch  are  exceedingly  poor  in 
oil,  averaging  about  0.25  percent,  if  we  disregard  the  tip  starch  in  Ear 
No.  3,  which  appears  to  have  absorbed  some  oil  directly  from  the  germ 
which  it  adjoins  and  partially  surrounds.  The  hulls  contain  slightly  less 
than  1  percent  of  oil  and  the  tip  caps  slightly  more  than  1  percent,  and 
it  is  quite  possible  that  this  oil  may  have  been  obtained,  in  part  at  least, 
by  absorption  from  the  horny  gluten  and  germ.  Indeed,  it  seems  highly 
probable  that  practically  all  of  the  true  oil  in  the  corn  kernel  is  originally 
deposited  in  the  germ  and  horny  gluten,  and  that  the  small  percentage 
or  mere  trace,  which  is  found  in  the  other  parts  is  largely  obtained  by 
absorption.  That  such  absorption  actually  does  occur  is  definitely 
proven  by  the  fact  that  the  percentage  of  oil  in  hominy  and  hominy 
products  increases  with  the  age  of  the  corn  used  in  the  milling.  (Hominy 


*New  Jersey  Agricultural  Experiment  Station  Bulletin  (1894),  105. 


1903.]  THE  STRUCTURE  OF  THE  CORN  KERNEL.  85 

consists  largely  of  the  horny  starch  with  more  or  less  adhering  white 
starch.) 

It  may  be  of  interest  to  state  in  this  connection  that  in  1866  Haber- 
landt*  discovered  with  the  microscope  that  the  germ  of  the  corn  kernel 
contains  a  large  amount  of  oil.  He  observed  no  oil  in  the  remaining  por- 
tions of  the  kernel.  By  chemical  analysis  Lenz*  found,  however,  that 
after  the  germs  were  removed  the  remaining  portion  of  the  kernel  con- 
tained 1.57  per  cent  of  oil.  These  results  were  fully  confirmed  by  Doctor 
Atwaterf  who  found  1.63  per  cent,  of  oil  in  the  corn  after  removing  the 
germs  and  adjoining  material,  although  neither  Lenz  nor  Atwater  appear 
to  have  ascertained  that  the  horny  gluten  (the  aleurone  layer)  contains 
the  chief  percentage  of  oil  outside  of  the  germ. 

By  further  reference  to  Table  1,  it  will  be  observed  (1)  that  the  germ 
contains  about  10  percent  of  ash  or  mineral  matter;  (2),  that  this  is  about 
ten  times  the  average  percentage  of  ash  contained  in  the  other  parts ;  and 
(3),  that  the  percentage  of  ash  in  the  different  parts  varies  with  the  per- 
centage of  oil,  to  quite  a  noticeable  degree. 

Of  course  the  percentage  of  carbohydrates  (starch,  cellulose,  pento- 
sans,  etc.)  varies  inversely  as  the  sum  of  the  other  constituents,  being 
about  35  percent  in  the  germ,  70  percent  in  the  horny  gluten,  and  from 
90  to  95  percent  in  the  other  principal  parts. 

The  marked  degree  of  uniformity  in  the  entire  percentage  composition 
of  the  germs  from  each  of  these  three  ears,  whether  low  protein,  medium 
protein,  or  high  protein,  seems  especially  noteworthy.  The  percentage 
of  protein  varies  only  from  19.56  to  19.91;  the  oil  from  33.71  to  36.54; 
the  ash  from  9.90  to  10.48;  and  the  carbohydrates  from  33.07  to  36.73. 
It  will  also  be  noted  that  the  percentages  of  both  protein  and  oil  are 
lower  in  the  germs  from  high  protein  corn  than  in  those  from  the  low 

protein  corn,  although  the  differences  are  not  marked. 

• 

MATHEMATICAL  DISTRIBUTION  OF  WASTE. 

It  will  be  borne  in  mind  that  in  making  the  mechanical  separations, 
in  order  to  obtain  each  of  the  seven  different  parts  in  pure  condition, 
unmixed  with  any  other  part,  there  was  necessarily  some  waste  product. 
This  waste  substance  amounted  to  about  20  per  cent  of  the  whole.  As 
has  already  been  explained,  this  mixed  waste  material  consists  of  only 
three  distinctly  different  parts — horny  gluten,  horny  starch,  and  white 
starch  (from  crown  and  tip),  the  other  three  parts — tip  caps,  hulls,  and 
germs,  being  easily  separated  completely  and  in  pure  form. 


*Allgempine  land— und  forstwirtschaftliche  Zeitung  (1866),  257;  Jahresbericht 
(Hoffman)  uber  die  Agricultur-f  hemie  (1866),  9,  106. 

tThesis,  Yale  College  (1869);  American  Journal  of  Science  and  Arts  (1869)  (2), 
48,  352. 


86  BULLETIN  No.  87.  [August, 

By  a  simple  computation  the  mixed  waste  material  can  be  distributed 
among  the  respective  parts  of  which  it  is  composed,  provided  we  may  be 
allowed  to  make  the  assumption  (which  is  approximately  the  truth)  that 
the  horny  starch  and  white  starch  are  present  in  the  waste  material  in  the 
same  proportions  as  they  are  in  the  pure  separated  portions.  Any  error 
which  might  be  introduced  by  following  this  assumption  would  have  but 
little  effect  because  the  composition  of  the  horny  starch  and  white  starch 
are  not  very  markedly  different  (the  protein  differs  by  2  to  3  percent) ; 
and  also  because  the  total  amount  of  waste  material  to  be  distributed  is 
only  from  one-third  to  one-half  the  sum  of  the  separated  horny  starch  and 
white  starch. 

It  will  be  observed  (see  Table  1)  that  the  mixed  waste  is  always  richer 
in  protein  than  the  horny  starch,  thus  showing  that,  besides  horny  starch 
and  white  starch,  it  also  contains  more  or  less  horny  gluten,  which,  of 
course,  we  know  to  be  the  fact. 

If  in  100  grams  of  corn  we  let 
x  equal  the  number  of  grams  of  tip  starch, 

Bx  equal  the  number  of  grams  of  crown  starch, 

Cx  equal  the  number  of  grams  of  horny  starch, 
y  equal  the  number  of  grams  of  horny  gluten,  and 
<S  equal  the  sum  of  these  four  parts,  then 

(1)  x  +  Bx  +  Cx  +  y=S 
Now  if  we  let 

a  equal  the  per  cent  of  protein  in  the  tip  starch, 

b  equal  the  per  cent  of  protein  in  the  crown  starch, 

c  equal  the  per  cent  of  protein  in  the  horny  starch, 

d  equal  the  per  cent  of  protein  in  the  horny  gluten,  and 

s  equal  the  number  of  grams  of  protein  in  all  of  these  four  parts,  then 

(2)  ax  +  bBx  +  cCx  +  dy=s 

Thus  we  have  two  equations  with  which  to  solve  for  x  and  y,  which  are 
the  only  unknown  quantities,  B  and  C  being  factors  which  can  be  ob- 
tained by  dividing  the  percents  of  separated  crown  starch  and  horny 
starch,  respectively,  by  that  of  tip  starch,  and  S  being  the  sum  of  the 
separated  tip  starch,  crown  starch,  horny  starch,  horny  gluten  and  mixed 
waste,  as  given  in  Table  1 ;  and  a,  b,  c,  d,  being  the  respective  percentages 
of  protein  in  the  four  separated  materials,  tip  starch,  crown  starch,  horny 
starch,  and  horny  gluten,  and  s  being  the  total  number  of  grams  of  pro- 
tein contained  in  these  four  separated  parts  and  in  the  mixed  waste,  all 
of  which  data  are  also  given  in  Table  1. 

PHYSICAL  COMPOSITION  OF  THE  CORN  KERNEL. 

From  the  above  computations  we  obtain  the  results  given  in  Table  2, 
which  gives  the  total  percentages  of  each  of  the  seven  different  parts  con- 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


tained  in  the  corn  kernel  (counting  crown  starch  and  tip  starch  as  tw« 

parts),  and  with  no  waste  material. 

TABLE  2. — TOTAL  PERCENTAGES  OF  THE  DIFFERENT  PARTS  OF  THE  CORN  KERNEL. 


Name  of  parts. 

Ear  No.  1, 
(low 
protein). 

Ear  No.  2, 
(medium 
protein). 

Ear  No.  3, 
(high 
protein). 

Tip  caps  

1.20 

1  46 

1  62 

Hulls  

5.47 

5  93 

6  09 

Horny  gluten  

11  61 

8  51 

13  32 

Horny  starch  

37  15 

47  08 

44  89 

Crown  starch  

21  26 

17  01 

13  88 

Tip  starch  

13  71 

8  48 

6  28 

Germs  

9  59 

11  53 

11  93 

Total  . 

99  99 

100  00 

100  01 

It  will  be  observed  that  the  percentages  of  horny  gluten,  horny  starch, 
and  germs  are  noticeably  higher  in  the  high  protein  corn  than  in  the  low 
protein  corn;  while  the  opposite  is  true  with  the  white  starch,  the  per- 
centages of  crown  starch  and  tip  starch  being  markedly  higher  in  the  low 
protein  corn  than  they  are  in  the  high  protein  corn.  It  is  noteworthy 
that  the  horny  gluten  in  high  protein  corn  not  only  contains  a  higher  per- 
centage of  protein  than  the  germs,  but  that  the  proportion  of  horny 
gluten  in  the  kernel  equals  or  exceeds  that  of  the  germs.  The  only  dis- 
crepancies appearing  in  Table  2  are  the  low  percentage  of  horny  gluten 
and  the  high  percentage  of  horny  starch  in  Ear  No.  2.  Otherwise  the 
percentages  of  parts  in  the  medium  protein  ear  are  always  intermediate 
between  those  in  the  other  two  ears,  as  would  be  expected.  Even  these 
discrepancies  disappear  if  the  two  horny  parts  be  added  together  and 
considered  as  one  part,  as  is  done  in  the  practical  work  of  selecting  seed 
corn  for  higher  protein  content  by  mechanical  examination,  as  will  be  seen 
by  referring  to  Table  3. 

TABLE  3. — PERCENTAGES  OF  THE  DIFFERENT  PARTS  OF  THE  CORN  KERNEL  AS 
COMMONLY  OBSERVED  IN  MECHANICAL  EXAMINATION  FOR  SEED 
CORN  SELECTION. 


Names  of  parts. 

Ear  No.  1, 
(low 
protein). 

Ear  No.  2, 
(medium 
protein). 

Ear  No.  3, 
(high 
protein). 

Average 
percent. 

Tip  caps  

1  20 

1  46 

1  62 

1  43 

Hulls  

5  47 

5  93 

6  09 

5  83 

Horny  part  

48.76 

55.59 

58.21 

54.19 

White  starch  

34.96 

25.49 

22.16 

27.54 

Germs  

9.59 

11.53 

11.93 

11.02 

Total  .      . 

99  98 

100  00 

100  01 

100  00 

88  BULLETIN  No.  87.  [August, 

In  this  table  the  crown  starch  and  tip  starch  are  also  added  together 
and  the  sum  recorded  as  white  starch.  The  increase  in  the  amount  of 
horny  part  (from  48.76  to  58.21  percent),  and  the  decrease  in  white 
starch  (from  34.96  to  22.16  percent)  as  we  pass  from  the  low  protein  to 
the  high  protein  corn,  is  plainly  apparent. 

DISTRIBUTION  OF  CHEMICAL  CONSTITUENTS. 

Table  4  shows  the  location  or  complete  distribution  of  the  chemical 
constituents  among  the  seven  different  physical  parts  of  the  corn  kernel. 
In  other  words,  this  table  represents  the  separation  of  100  grams  (or  100 
pounds)  of  corn  into  seven  different  structural  or  physical  parts,  and  the 
subsequent  division  of  each  of  these  parts  into  the  four  chemical  con- 
stituents, protein,  oil,  ash,  and  carbohydrates. 

The  complete  data  shown  in  Table  4  are  presented  especially  for  the 
benefit  of  farmers  who  are  corn  breeders,  and  also  for  the  benefit  of 
the  manufacturers  of  corn  products.  The  agreement  between  the  sum 
of  the  separate  determinations  and  the  direct  determinations  of  the  same 
constituent  in  the  whole  corn  is  very  satisfactory,  considering  that  these 
results  are  obtained  by  computation  from  the  analyses  of  nine  different 
materials,  including  the  whole  corn.  The  greatest  difference  is  well 
within  the  limit  of  unavoidable  error  in  sampling  and  analytical  deter- 
minations. A  careful  study  of  this  table  will  reveal  some  interesting  and 
valuable  facts.  For  example,  it  will  be  seen  that  in  100  pounds  of  the 
low  protein  corn  the  horny  gluten  contains  only  2.23  pounds  of  protein; 
while  3.27  pounds  of  protein  are  contained  in  the  horny  gluten  in  100 
pounds  of  the  high  protein  corn.  Again,  in  100  pounds  of  the  low  pro- 
tein corn  the  horny  starch  contains  only  3.02  pounds  of  protein;  while 
4.93  pounds  of  protein  are  contained  in  the  horny  starch  in  100  pounds  of 
the  high  protein  corn. 

On  the  other  hand,  in  100  pounds  of  the  low  protein  corn  the  crown 
starch  and  tip  starch  contain  1.53  and  .84  pounds  of  protein,  respectively; 
while  1.20  and  .60  are  the  respective  amounts  contained  in  the  correspond- 
ing parts  of  the  high  protein  corn. 

If  we  add  together  the  horny  parts  and  then  add  together  the  crown 
starch  and  tip  starch,  as  is  done  in  the  practical  selection  of  seed  corn  by 
mechanical  examination,  we  obtain  the  results  shown  in  Table  5. 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


TABLE  4. — PHYSICAL  AND  CHEMICAL  DISTRIBUTION  OF -100  GRAMS  (OR  100  POUNDS) 

OF  CORN. 


Ear  No.  1  (low  in  protein). 


Names  of  parts. 

Physical 
distribution 
(grams  or 
pounds). 

Chemical  distribution. 

Protein, 
(grams  or 
pounds). 

Oil, 
(grams  or 
pounds). 

Ash, 
(grams  or 
pounds')  . 

Carbo- 
hydrates, 
(grams  or 
pounds). 

Tip  caps  .  . 

1.20 
5.47 

11.61 
37.15 

21.26 
13.71 

9.59 

.09 
.27 

2.23 
3.02 

1.53 

.84 

1.91 

.01 
.05 

.46 
.06 

.04 
.04 

3.50 

.01 
.04 

.11 
.07 

.07 
.04 

1.01 

1.09 
5.10 

8.81 
34.01 

19.62 
12.79 

3.17 

Hulls  

Horny  gluten  

Horny  starch  .      .    . 

Crown  starch  

Tip  starch  

Germs  

Total  

99.99 

9.89 
9.28 

4.16 
4.20 

1.35 
1.41 

84.59 
85.11 

Whole  corn.  . 

Ear  No.  2  (medium  in  protein). 


Tip  caps  

1.46 

.13 

.03 

.02 

1.28 

Hulls  

5.93 

.23 

.05 

.05 

5.60 

Horny  gluten  

8  51 

1  89 

.59 

.15 

5.88 

Horny  starch  

47.08 

4.80 

.11 

.11 

42.05 

Crown  starch  .   .    .  . 

17  01 

1  35 

03 

.04 

15.59 

Tip  starch  

8.48 

.65 

.03 

.03 

7.77 

Germs  

11  53 

2  28 

4.02 

1.14 

4.09 

Total  

100  00 

11  33 

4  86 

1.54 

82.26 

Whole  corn  

10  95 

4.33 

1.55 

83.17 

Ear  No.  3  (high  in  protein). 


Tip  caps  

1  62 

.08 

.03 

.03 

1.48 

Hulls  

6  09 

23 

.05 

.07 

5.74 

Horny  gluten  

13  32 

3  27 

61 

23 

9  20 

Horny  starch  . 

44  89 

4  93 

10 

09 

39  76 

Crown  starch  

13  88 

1  20 

07 

.05 

12.56 

Tip  starch  ... 

8  28 

60 

11 

.05 

7.51 

Germs  

11  93 

2  33 

4  02 

1   19 

4.38 

Total  

100  01 

12  64 

4  99 

1.71 

80.63 

Whole  corn  

12.85 

5.36 

1.67 

80.12 

90 


BULLETIN  No.  87. 


[August, 


TABLE  5. — POUNDS  OF  PROTEIN  IN  100  POUNDS  OF  CORN. 


Names  of  parts. 

Low 
protein 
corn. 

Medium 
protein 
corn. 

High 
protein 
corn. 

In  tip  caps  .                   .        

.09 

.13 

.08 

In  hulls  

.27 

.23 

.23 

In  horny  part  

5.25 

6.69 

8.20 

In  white  starch                                            

2.37 

2.00 

1.80 

In  germs  

1.91 

2.28 

2.33 

Total  .     

9.89 

11.33 

12.64 

It  will  be  observed  that  the  increase  in  protein  in  high  protein  corn 
over  that  in  low  protein  corn  occurs  almost  entirely  in  the  horny  part  of 
the  corn  kernel.  As  indicated  in  previous  bulletins  there  is  also  a  slight 
increase  in  protein  in  the  germ,  although  this  is  quite  insignificant  as  com- 
pared with  the  increase  in  the  horny  part.  In  passing  from  low  protein 
corn  to  high  protein  corn,  there  is  an  appreciable  decrease  in  the  amount 
of  protein  contained  in  the  white  starch.  Of  course  this  is  due  to,  the 
marked  decrease  in  the  actual  amount  of  white  starch  in  high  protein 
corn.  Indeed,  this  decrease  in  the  quantity  of  white  starch  is  even  more 
marked  than  would  appear  from  Table  5,  because  the  white  starch  in  the 
high  protein  corn  is  actually  richer  in  protein  than  that  in  low  protein 
corn,  as  would  be  expected  and  as  is  shown  in  Table  1. 

The  data  given  in  Table  5  strongly  confirm  the  results  which  we  have 
already  obtained  in  practical  experience  in  corn  breeding.  For  example, 
we  have  been  breeding  both  high  protein  corn  and  low  protein  corn  for 
the  past  seven  years.  In  the  high  protein  corn  we  find  that  the  propor- 
tion of  horny  part  has  increased  very  markedly,  while  the  white  starchy 
part  has  markedly  decreased.  In  the  low  protein  corn  the  opposite  is 
true,  the  horny  part  having  decreased  and  the  white  starchy  part  having 
markedly  increased,  in  proportion. 

By  computation  from  the  data  given  in  Table  4,  we  have  constructed 
Table  6,  which  shows  the  percentage  distribution  of  the  different  chemical 
constituents  among  the  several  physical  parts  of  the  corn  kernel. 

It  will  be  seen  that  as  an  average  about  22  percent  of  the  total  protein 
is  contained  in  the  horny  gluten,  nearly  40  percent  in  the  horny  starch, 
and  nearly  20  percent  in  the  germ,  thus  these  three  parts  contain  about 
80  percent  of  the  total  protein  in  the  kernel. 

The  germ  contains  from  80  to  84  percent  of  the  oil,  while  all  other 
parts  combined  contain  only  15  to  20  percent  of  the  total  oil  in  the 
kernel.  Based  upon  this  fact  is  the  method  for  selecting  high  oil  or  low 
oil  seed  corn  by  mechanical  examination,  the  ears  whose  kernels  show  a 
large  proportion  of  germ  being  high  oil  corn  and  those  with  small  germs 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


91 


TABLE  6. — PERCENTAGE  DISTRIBUTION  OF  CHEMICAL  CONSTITUENTS  AMONG 

PHYSICAL  PARTS. 


Ear  No.  1  (low  in  protein). 


Names  of  parts. 

Percent 
of  total 
protein. 

Percent 
of  total 
oil. 

Percent 
of  total 
ash. 

Percent 
of  total 
carbo- 
hydrates. 

In  tip  caps  .          

.89 

33 

81 

1  29 

In  hull        ...                 

2  75 

1  21 

3  34 

6  03 

In  horny  gluten.. 

22  56 

11   13 

7  96 

10  41 

In  horny  starch  

30.51 

1.43 

4  98 

40  22 

In  crown  starch  

15.52 

.97 

5  07 

23  18 

In  tip  starch                                  .... 

8.46 

95 

2  96 

15  12 

In  germs  .                                           .  . 

19  31 

83  99 

74  87 

3  75 

Total  

100.00 

100.01 

99  99 

100  00 

Ear  No.  2  (medium  in  protein). 


In  tip  caps  

1.14 

.69 

1.06 

1  56 

In  hull   

2.07 

1  08 

3  06 

6  80 

In  horny  gluten.. 

16  67 

12  21 

9  56 

7  15 

In  horny  starch  

42.36 

2.32 

7.38 

51.12 

In  crown  starch.. 

11.88 

.59 

2.67 

18.96 

In  tip  starch 

5.75 

.68 

1.72 

9.45 

In  germs  . 

20.14 

82.43 

74.55 

4.97 

Total  .. 

100.01 

100.00 

100.00 

100.01 

Ear  No.  3  (high  in  protein). 


In  tip  caps  .          ... 

59 

65 

1  76 

1  84 

In  hull  

1.85 

.93 

3.90 

7.12 

In  horny  gluten  

25  88 

12  29 

13  49 

11.41 

In  horny  starch  

39  00 

1   98 

5  49 

49.31 

In  crown  starch  

9  45 

1   44 

2  99 

15  58 

In  tip  starch      

4  77 

2  25 

2  89 

9  32 

In  germs  .    .      .    . 

18  45 

80  46 

69  46 

5  43 

Total  . 

99  99 

100  00 

99  98 

100  01 

92 


BULLETIN  No.  87. 


[August, 


low  oil  corn.  (See  Plate  4.)  About  12  percent  of  the  total  oil  is  con- 
tained in  the  horny  gluten,  leaving  only  about  5  percent  of  the  oil  dis- 
tributed among  the  remaining  five  physical  parts,  and,  as  stated  above, 
more  or  less  of  this  small  amount  is  undoubtedly  absorbed  from  the  con- 
tiguous germ  or  horny  gluten. 

It  will  be  noted  that  the  ash  is  closely  associated  with  the  oil,  nearly 
75  percent  of  the  total  ash  being  contained  in  the  germ,  and  about  10 
percent  in  the  horny  gluten,  as  an  average. 

Table  7  shows,  for  direct  comparison,  the  percentage  distribution  of  the 
protein  among  the  different  physical  parts,  in  each  ear,  the  two  horny 
parts,  and  also  the  two  white  starchy  parts,  being  combined,  as  in  Table  5. 

TABLE  7. — DISTRIBUTION  OP  100  GRAMS  (OR  100  POUNDS)  OF  PROTEIN  AMONG  THE 
PHYSICAL  PARTS  AS  OBSERVED  IN  MECHANICAL  EXAMINATION. 


Names  of  parts. 

Low 
protein 
Corn. 

Medium 
protein 
corn. 

High 
protein 
corn. 

In  tip  caps  ...                 .    . 

89 

1   14 

59 

In  hulls  . 

2  75 

2  07 

1  85 

In  horny  part  

53  07 

59  03 

64  88 

In  white  starch     

23  98 

17  63 

14  22 

In  germs  .    .        ... 

19  31 

20  14 

18  45 

Total  

100  00 

100  01 

99  99 

Table  7  illustrates  very  plainly  the  fact  that,  as  we  pass  from  low  pro- 
tein corn  to  high  protein  corn,  the  protein  decreases  in  the  white  starchy 
part  and  increases  in  the  horny  part;  in  other  words,  in  breeding  corn  for 
high  protein,  we  decrease  the  white  starchy  part,  which  is  comparatively 
poor  in  protein,  and  increase  the  horny  part,  which  averages  very  much 
richer  in  protein,  the  horny  starch  containing  2  to  3  percent  more  pro- 
tein than  the  white  starch,  and  the  horny  gluten  being  richer  in 
protein  than  any  other  part  of  the  kernel.  As  a  rule,  in  breeding  for 
high  protein  there  is  also  a  slight  increase  in  the  proportion  of  germ, 
which,  being  rich  in  protein,  adds  somewhat  to  the  increase  in  protein. 

MECHANICAL  METHODS  OF  SELECTING  SEED  CORN  FOR 
IMPROVEMENT  IN  COMPOSITION. 

As  has  already  been  shown  in  our  Bulletin  No.  82  "Methods  of  Corn 
Breeding,"  we  have  found  it  entirely  feasible  and  practical  to  select  seed 
corn  of  higher  protein  content  by  a  simple  mechanical  examination  of  a 
few  kernels  from  each  ear.  With  some  care  any  farmer  or  corn  grower 
can  learn  to  pick  out  high  protein  seed  corn  by  dissecting  and  examining 
a  few  kernels  from  each  ear  (by  means  of  a  pocket-knife),  selecting  for 
high  protein  seed  the  ears  whose  kernels  show  a  large  proportion  of  horny 


1903.]  THE  STRUCTURE  OF  THE  CORN  KERNEL.  93 

part,  and  rejecting  those  showing  a  small  proportion  of  horny  part.     (See 
Plate  3;  also  Plates  1  and  2.) 

HIGH  PROTEIN  KERNELS  Low  PROTEIN  KERNELS 

(Much  horny  part;  (Little  horny  part; 

little  white  starch).  much  white  starch). 


PLATE  3. 


94  BULLETIN  No.  87.  [August, 

This  method  is  already  in  use  by  practical  corn  breeders,  and  with  a 
very  satisfactory  degree  of  success.  For  example,  in  selecting  seed  corn 
by  this  method  Mr.  Ralph  Allen,  of  Tazewell  County,  obtained  seed  ears 
for  the  year  1902,  which  were  1.46  percent  higher  in  protein  than  the 
rejected  ears  from  the  same  lot,  and  for  this  season  (1903)  his  selected 
seed  ears  contain  1.58  percent  protein  more  than  the  ears  which  he  has 
rejected.  In  other  words,  his  selected  seed  corn  is  richer  by  1.58  pounds 
of  protein  per  100  pounds  of  corn  than  that  rejected. 

The  method  proposed  some  years  ago  by  Professor  Willard,  Director  of 
the  Kansas  Agricultural  Experiment  Station,  of  picking  out  high  protein 
seed  by  simply  selecting  for  large  germs  enables  one,  as  a  rule,  to  make 
some  gain  in  protein,  but  the  gain  is  very  much  greater  when  the  propor- 
tion of  horny  part  is  considered.  In  fact,  from  our  own  experience  we 
find  that  the  selection  for  a  large  proportion  of  horny  part  is  a  very  much 
more  trustworthy  index  than  the  size  of  the  germ,  in  securing  high  pro- 
tein seed,  and  we  often  find  corn  with  large  germs  which  is  actually  low 
in  protein,  because  of  a  small  percentage  of  protein  in  the  remainder  of 
the  kernel.  The  fact  that  only  20  percent  of  the  total  protein  of  the 
kernel  is  obtained  in  the  germ  (as  shown  in  Table  7)  is  evidence  of  the 
uncertainty  of  obtaining  high  protein  seed  corn,  and  of  the  improbability 
of  making  any  very  considerable  gain  in  protein,  by  this  method  of  selec- 
tion. This  difficulty  was  well  understood  by  Professor  Willard,  as  will 
be  seen  in  the  following  quotation  from  the  Kansas  Experiment  Station 
Bulletin  No.  107,  page  63. 

"  There  are  undoubtedly  great  differences  in  the  protein  content  of  the 
part  of  the  kernel  exclusive  of  the  germ,  and  it  is  conceivable  and  not 
improbable,  that  a  large  germ,  though  in  itself  tending  to  produce  high 
protein  content  might  be  overcome  by  the  low  protein  of  the  remainder 
of  the  kernel."* 

Of  course,  if  one  picks  out  corn  with  large  germs  and  at  the  same  time, 
either  consciously  or  unconsciously,  selects  those  ears  whose  kernels  con- 
tain a  large  proportion  of  horny  part,  he  may  make  considerable  gain  in 
protein,  but  in  such  case  the  gain  should  not  be  attributed  solely  to  the 
large  germs. 


*  Protein  is  substituted  for  nitrogen  in  this  quotation. 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


95 


HIGH  OIL  KERNELS 
(Large  germs). 


Low  OIL  KERNELS 
(Small  germs). 


PLATE  4. 


The  method  of  selecting  seed  corn  for  high  oil  content  on  the  basis  of 
large  germs  (see  Plate  4)  is  certainly  well  founded,  because  of  the  fact  that 
more  than  80  percent  of  the  total  oil  of  the  kernel  is  contained  in  the  germ. 


96 


BULLETIN  No.  87. 


[August, 


THE  CORRELATION  OF  SOME  PHYSICAL  PARTS  AND  CHEMICAL 
CONSTITUENTS  OF  THE  CORN  KERNEL. 

As  was  clearly  shown  in  our  Bulletin  No.  55,  there  is  usually  a  marked 
correlation  between  the  percentage  of  germ  and  the  percentage  of  oil  in 
the  corn  kernel,  as  will  be  seen  from  the  following  summary  of  100  sep- 
arate determinations  reported  in  that  bulletin : 

TABLE  No.  8. — CORRELATION  BETWEEN  GERM  AND  OIL  IN  CORN  KERNELS. 


Number  of  determinations. 

Small  germ  corn. 

Large  germ  corn. 

Germ, 
percent. 

Oil, 
percent. 

Germ, 
percent. 

Oil, 
percent. 

10  

9  10 
8  56 
8.28 
8.73 
9  82 

3.58 
3.22 
3.64 
3.32 
4.30 

14.11 
12.40 
12.01 
13.30 
11.06 

6.49 
6.71 
6.08 
5.82 
5.21 

10  

10  

10   

10  

General  average  ...... 

8.90 

3.61 

12.57 

6.06 

While  there  is,  of  course,  some  variability  due  in  part  to  the  different 
percentages  of  oil  in  germs  from  different  kernels  (especially  in  kernels 
from  different  ears)  and  in  part  to  the  different  percentages  of  oil  in  the 
horny  gluten  (and  to  some  extent  in  other  parts)  from  different  ears  (see 
Table  2),  nevertheless  it  will  be  observed  that  there  is  a  marked  correla- 
tion between  the  percentage  of  germ  and  the  percentage  of  oil  in  the  corn 
kernel.  In  other  words,  the  percentage  of  oil  varies  with  the  percentage 
of  germ.  It  will  be  observed,  however,  that  a  high  percentage  of  germ  is 
accompanied  by  a  still  higher  proportionate  percentage  of  oil,  indicating 
that  increased  proportion  of  germ  in  the  kernel  is  due  to  an  increase  in  the 
quantity  of  oil  more  largely  than  of  the  remainder  of  the  germ. 

CORRELATION  BETWEEN  OIL  AND  PROTEIN. 

That  there  is  a  marked  correlation  between  the  percentages  of  germ 
and  oil  in  the  corn  kernel  is  certainly  well  established;  consequently,  if 
the  proportion  of  germ  were  a  reliable  index  to  the  relative  protein  con- 
tent of  the  kernel,  there  would,  of  course,  be  some  marked  correlation  be- 
tween the  percentages  of  oil  and  protein  in  corn. 

In  Table  1  of  Bulletin  No.  55  are  recorded  the  proximate  analyses  of 
163  different  ears  of  corn.  Table  9  is  derived  from  that  data,  and  shows 
the  percentages  of  oil  and  protein  contained  in  the  ten  ears  which  are 
lowest  in  oil  and  in  the  ten  ears  which  are  highest  in  oil,  the  analyses  being 
arranged  in  the  descending  order  for  protein. 

The  correlation  between  oil  and  protein  is  certainly  very  slight.  In 
the  low  oil  corn  the  oil  varies  from  only  3.84  to  4.08  percent,  while  the 
protein  varies  from  9.08  to  12.96  percent.  In  the  high  oil  corn  the  oil 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


97 


varies  only  from  5.46  to  6.02,  while  the  protein  varies  from  9.58  to  13.87 
percent,  making  a  difference  of  4.29  percent  protein  between  these  ex- 
treme ears,  while  the  difference  in  oil  is  only  .09  percent  between  the 
same  ears.  The  average  percentages  of  oil  in  these  two  lots  of  corn  vary 
from  3.99  to  5.64  percent,  while  the  corresponding  averages  for  protein 
are  11.02  and  11.19,  thus  showing  very  little  correlation  between  the  per- 
centages of  oil  and  protein  in  the  corn  kernel. 

TABLE  9. — CORRELATION  BETWEEN  OIL  AND  PROTEIN  IN  THE  CORN  KERNEL. 


Low  oil  corn. 

High  oil  corn. 

Oil, 

Protein, 

Oil, 

Protein, 

percent. 

percent. 

percent. 

percent. 

3  97 

12.96 

5.72 

13.87 

3.99 

12.28 

5.51 

13.10 

4  03 

11.71 

5  61 

12.09 

4.07 

11.49 

5.75 

11.18 

3.84 

11.29 

5  65 

10.82 

4  08 

11.29 

5.51 

10  49 

3.94 

10.97 

5.46 

10.32 

4.01 

9.68 

5.51 

10.23 

3  95 

9.44 

6  02 

10.18 

4.05 

9.08 

5  63 

9.58 

AveragesS  .  99 

11.02 

5.64 

11.19 

Table  10  is  also  derived  from  Table  1  of  Bulletin  No.  55,  and  is  similar 
to  Table  9,  except  that  the  analyses  of  the  ten  ears  lowest  in  protein  and 
of  the  ten  ears  highest  in  protein  are  chosen.  This  shows  the  reverse 
correlation ;  that  is,  between  protein  and  oil.  Of  course,  the  results  should 
be  practically  the  same  as  shown  in  Table  9,  the  chief  value  of  Table  10 
being  that  it  uses  almost  an  entirely  different  set  of  analyses,  and  con- 
sequently gives  a  duplicate  illustration  of  the  lack  of  correlation  between 
these  two  constituents. 

TABLE  10. — CORRELATION  BETWEEN  PROTEIN  AND  OIL  IN  THE  CORN  KERNEL. 


Low  protein  corn. 

High  protein  corn. 

Protein, 

Oil, 

Protein, 

Oil, 

percent. 

percent. 

percent. 

percent. 

9  31 

4.96 

13  87 

5.72 

8  40 

4.91 

13  10 

5.51 

8  38 

4.88 

12  68 

5.29 

9  31 

4.82 

12  81 

5.21 

8  25 

4.81 

12  63 

5.15 

9  22 

4.60 

13  06 

4.93 

9   15 

4.55 

12  57 

4.82 

9  30 

4.38 

12  79 

4.25 

9   12 

4.10 

12  76 

4.10 

9  08 

4.05 

12.96 

3.97 

Averages...  8.  95 

4.61 

12.92 

4.90 

BULLETIN  No.  87. 


[August, 


It  will  be  observed  that,  although  the  averages  for  protein  vary  from 
8.95  to  12.92  percent,  the  averages  for  oil  vary  only  from  4.61  to  4.90  per- 
cent. These  averages  indicate  only  a  slight  correlation  between  protein 
and  oil,  and  the  analyses  of  the  individual  ears  show  that  even  this  cor- 
relation is  by  no  means  constant. 

In  connection  with  some  investigations  relative  to  heredity  Professor 
Frank  Smith  of  this  University,  has  prepared  correlation  tables  (see 
Tables  11  and  12)  from  the  163  analyses  of  individual  ears  of  corn  recorded 
in  Table  1  of  Bulletin  No.  55.  Table  11  shows  the  correlation  between 

TABLE  11. — ONE  HUNDRED  SIXTY-THREE  EARS  OF  CORN  GROUPED  ACCORDING  TO 
PERCENTAGES  OF  PROTEIN  AND  CARBOHYDRATES. 


Carbo- 
hydrates 
percent. 

Protein,  percent. 

Total 
No.  of 
ears. 

8 

8.5 

9 

9.5 

10 

10  5 

II 

11.5 

12 

12.5 

13 

13  5 

14 

79 

1 

1 

79  5 

80 

1 

1 

80.5 

1 

2 

3 

81 

1 

3 

4 

81.5 

1 

2 

7 

3 

13 

82 

2 

5 

13 

20 

82.5 

1 

3 

7 

12 

3 

1 

27 

83 

2 

7 

16 

7 

32 

83.5 

2 

7 

9 

4 

1 

23 

84 

3 

7 

5 

1 

16 

84  5 

1 

8 

2 

11 

85 

1 

5 

6 

85.5 

1 

2 

2 

1 

19 

6 

Total 
No.  of 
ears. 

1 

2 

4 

19 

24 

31 

25 

19 

12 

6 

1 

163 

The  correlation  of  high  protein  with  low  carbohydrates  and  vice  versa  equals 
90.05  per  cent. 

protein  and  carbohydrates,  the  entire  163  ears  of  corn  being  grouped  ac- 
cording to  the  percentage  of  protein  and  carbodydrates  which  they  con- 
tain. This  table  well  illustrates  what  is  meant  by  a  high  degree  of  cor- 
relation. With  an  increasing  protein  percentage  there  is  a  decreasing 
percentage  of  carbohydrates,  and  there  are  no  marked  exceptions  to  this 
rule.  Note,  for  example,  that  there  is  one  ear  containing  14  percent  of 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


99 


protein,  but  that  this  ear  contains  only  79  percent  of  carbohydrates, 
being  the  highest  in  protein  and  also  the  lowest  in  carbohydrates  of  the 
163  ears.  There  are  nineteen  ears  containing  only  12  percent  of  protein, 
but  none  of  these  nineteen  ears  contains  less  than  81  percent  of  carbo- 
hydrates; thirteen  of  them  contain  82  percent  of  carbohydrates,  while 
five  others  are  within  one-half  percent  of  that  amount.  One  ear  con- 
tains only  8  percent  of  protein,  but  this  ear  contains  85.5  percent  of 
carbohydrates,  being  both  the  lowest  in  protein  and  the  highest  in  carbo- 
hydrates of  the  163  ears.  It  will  be  observed  that  of  the  163  ears,  several 
groups  fall  in  the  squares  representing  low  protein  (8  to  10  percent)  and 
high  carbohydrates  (84  to  85.5  percent) ;  also  that  many  ears  fall  in  the 
squares  representing  high  protein  (12  to  14  percent)  and  low  carbo- 
hydrates (80  to  82  percent) ;  so  that,  including  the  ears  with  medium  con- 
tent of  protein  and  carbohydrates,  we  find  that  the  group  numbers  of  163 
ears  fall  almost  in  a  straight  line  extending  from  the  lower  left-hand  cor- 
ner to  the  upper  right-hand  corner  of  the  table.  It  will  be  seen  that  no 
ears  whatever  fall  in  the  squares  representing  high  protein  and  high  car- 
bohydrates, or  in  those  representing  low  protein  and  low  carbohydrates. 
By  mathematical  computation  Professor  Smith  has  found  that  we  have 
in  this  table  90.05  percent  of  a  perfect  correlation. 

TABLE  12. — ONE  HUNDRED  SIXTY-THREE  EARS  OF  CORN  GROUPED  ACCORDING  TO 
PERCENTAGES  OF  PROTEIN  AND  OIL. 


Oil, 
percent. 

Protein,  percent. 

Total 
No.  of 
ears. 

8 

85 

9 

95 

10 

10  5 

II 

115 

12 

12  5 

13 

13.5 

14 

38 

1 

1 

40 

2 

2 

2 

3 

1 

1 

1 

12 

4.2 

3 

2 

3 

3 

2 

3 

2 

18 

44 

8 

4 

2 

7 

3 

2 

21 

46 

2 

1 

1 

8 

5 

8 

4 

3 

32 

48 

1 

1 

5 

6 

3 

7 

2 

4 

5 

34 

50 

1 

2 

1 

3 

3 

5 

4 

1 

20 

52 

2 

3 

2 

2 

1 

3 

1 

14 

5.4 

2 

2 

5.6 

1 

1 

1 

1 

1 

1 

6 

58 

1 

1 

2 

6.0 

1 

1 

Total 
No.  of 
ears. 

1 

2 

4 

19 

19 

24 

31 

25 

19 

12 

6 

1 

163 

The  correlation  of  high  protein  with  high  oil  and  of  low  protein  with  low  oil 
equals  3.81  percent. 


100  BULLETIN  No.  87.  [August, 

Table  12  shows  the  degree  of  correlation  which  exists  between  oil  and 
protein.  It  will  be  seen  that  there  is  no  such  grouping  as  in  Table  11. 
In  other  words,  there  is  no  marked  correlation  between  the  oil  and  pro- 
tein in  corn.  Some  ears  are  rich  in  one  of  these  constituents  and  poor 
in  the  other;  other  ears  are  rich  in  both,  and  still  others  are  poor  in  both, 
so  that  the  grouping  of  the  numbers  of  ears  according  to  the  percentages 
of  oil  and  protein  which  they  contain  resembles  a  circle  much  more  nearly 
than  a  straight  line.  By  computation  it  is  found  that  there  is  a  slight 
tendency  for  the  protein  to  increase  with  increasing  oil  content,  but  the 
degree  of  correlation  amounts  to  only  3.81  percent  of  a  perfect  correlation. 

All  of  the  above  data  tend  to  prove  that,  as  the  percentage  of  protein 
increases  in  corn  the  starch  decreases,  while  the  oil  remains  almost  un- 
changed; and  that  we  may  increase  or  decrease  the  percentage  of  oil  or  of 
germ  in  corn  without  markedly  affecting  the  percentage  of  protein.  This 
was  the  conclusion  drawn  when  the  above-mentioned  163  ears  of  corn 
were  analyzed  more  than  six  years  ago.  The  different  strains  of  corn 
which  we  have  finally  produced  in  our  regular  corn  breeding  work  fur- 
nish us  excellent  material  for  ascertaining  what  effect  is  produced  upon 
the  oil  content  of  corn  by  breeding  for  a  higher  or  lower  protein  content; 
and,  vice  versa,  what  effect  is  produced  upon  the  protein  content  by  breed- 
ing for  a  higher  or  lower  oil  content. 

In  1900  we  planted  ten  field  rows  (called  the  "mixed  plot")  with  two 
kinds  of  corn  in  every  row,  one  kind  having  been  bred  for  four  years  for 
high  oil  content,  the  other  (originally  from  the  same  variety  and  stock) 
having  been  bred  during  the  same  four  years  for  low  oil  content.  These 
two  kinds  of  seed  were  planted  in  every  row  and  in  fact  in  every  hill, 
the  low  oil  kernels  and  the  high  oil  kernels  in  the  same  hill — just  far 
enough  apart  so  that  the  identity  of  the  individual  plants  could  be  known 
as  they  grew  during  the  season.  The  corn  from  each  of  the  ten  rows  was 
harvested  in  two  lots,  one  lot  being  corn  from  high  oil  seed  and  the  other 
lot  being  from  low  oil  seed.  The  two  lots  from  each  row  were  kept  sep- 
arate, the  one  being  labeled  as  corn  from  the  "  high  oil  side"  of  the  row 
and  the  other  from  the  "  low  oil  side." 

The  percentages  of  oil  and  of  protein  contained  in  these  different  lots 
of  corn  are  shown  in  Table  13. 

These  data  are  considered  very  reliable,  both  kinds  of  corn  having  been 
grown  during  the  same  season  and  in  exactly  the  same  soil  and  each  in- 
dividual sample  whose  composition  is  shown  in  Table  13  being  a  com- 
posite sample  representing  many  ears.  The  average  difference  in  oil 
content  between  the  high  oil  side  and  the  low  oil  side  is  1.97  percent  of 
oil,  while  the  average  difference  in  protein  is  0.18  percent.  Considering 
that  the  percentage  of  protein  in  the  corn  is  twice  as  large  as  the  per- 
centage of  oil,  it  will  be  seen  that  there  is  less  than  5  percent  of  a  perfect 
correlation  between  the  oil  and  protein. 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


101 


TABLE  13. — OIL  AND  PROTEIN  IN  CORN  HARVESTED  FROM  THE  "  MIXED  OIL" 

PLOT  IN  1900. 


Low  oil  side. 

High  oil  side. 

Row  No. 

Oil, 

Protein, 

Oil, 

Protein, 

percent. 

percent. 

percent. 

percent. 

1 

3.93 

10.07 

5.61 

10.06 

2 

3  78 

9.26 

5.74 

9.05 

3 

3  73 

10.21 

5  88 

9.12 

4 

3  75 

8.47 

5  99 

9.65 

5 

3.89 

9.39 

5  71 

10.08 

6 

3  80 

9.77 

5  91 

10.23 

7 

3  60 

9.80 

5  60 

9.91 

8 

3  58 

9.65 

5.84 

10.32 

9 

4  22 

9.18 

5.68 

9.15 

10 

3.27 

9.26 

5.82 

9.32 

Average  

3  81 

9.51 

5.78 

9.69 

COMPOSITION  OF  PEDIGREED  CORN. 

In  order  that  it  might  be  shown  with  even  more  absolute  certainty 
which  physical  part  of  the  corn  kernel  should  be  increased  in  order  to  in- 
crease the  protein  content,  or  the  oil  content,  etc.,  forty  ears  of  corn  were 
selected  from  the  1902  crop  from  our  oldest  breeding  plots,  ten  ears  being 
taken  from  each  of  four  different  strains,  namely : 

"  Illinois"  High  Protein  Corn. 

"  Illinois"  Low  Protein  Corn. 

"Illinois"  High  Oil  Corn. 

"Illinois"  Low  Oil  Corn. 

each  of  which  represents  the  seventh  generation  of  pedigreed  corn,  bred 
as  indicated  by  the  name.  Twenty-five  average  kernels  were  taken  from 
each  of  these  forty  ears,  the  germs  separated  from  the  remainder  of  the 
kernel  and  both  parts  (that  is,  germs  and  endosperms*)  analyzed  sepa- 
rately, for  each  ear,  another  sample  of  the  corn  from  each  ear  also  being 
analyzed  to  show  the  composition  of  the  whole  corn.  The  tabular  state- 
ments show  the  results  obtained. 

By  referring  to  Tables  14  and  15  it  will  be  seen  that  the  protein  con- 
tent of  the  low  protein  ears  varies  from  6.36  to  7.09  percent,  with  an  aver- 
age of  6.71  percent,  while  the  protein  content  of  the  high  protein  ears 
varies  from  13.98  to  15.01,  with  an  average  of  14.44  percent.  The 
average  oil  content  of  the  low  protein  corn  is  4.21  percent  and  of  the 
high  protein  ears  4.93  percent.  The  general  averages  indicate  a  slight 
correlation  between  oil  and  protein;  however,  there  are  several  of  the 
high  protein  ears  which  contain  less  oil  than  some  of  the  low  protein  ears, 
thus  showing  that  such  correlation  is  not  constant. 


*As  here  used  the  term  endosperm  includes  all  parts  of  the  kernel  except  the 
germ. 


102 


BULLETIN  No.  87. 


[August, 


TABLE  14. — CHEMICAL  COMPOSITION  OF  TEN  EARS  OF 
PROTEIN  CORN. 


ILLINOIS  "  Low 


Ear 
No. 

Protein, 
percent. 

Oil, 
percent. 

Ash, 
percent. 

Carbohydrates, 
percent. 

4276 

6.98 

4.69 

1.43 

86.90 

4281 

6.60 

4.21 

1.33 

87.86 

4286 

6.87 

4.16 

1.19 

87.78 

4287 

6.37 

3.90 

1.40 

88.33 

4295 

6.46 

4.14 

1.15 

88.25 

4313 

7.01 

4.13 

1.27 

87.59 

4321 

7.09 

3.84 

1.46 

87.61 

4328 

6.36 

4.05 

1.43 

88.16 

4346 

6.89 

4.33 

1.45 

87.33 

4368 

6.48 

4.67 

1.56 

87.29 

Average  . 

6.71 

4.21 

1.37 

87.71 

TABLE  15. — CHEMICAL  COMPOSITION  OF  TEN  EARS  OF  "ILLINOIS' 
PROTEIN  CORN. 


HIGH 


Ear 

Protein, 

Oil, 

Ash, 

Carbohydrates, 

No. 

percent. 

percent. 

percent. 

percent. 

4174 

14.70 

5.87 

1.48 

77.95 

4189 

14.74 

4.46 

1.70 

79.10 

4202 

14.21 

4.54 

1.50 

79.75 

4212 

14.61 

4.57 

1.66 

79.16 

4218 

14.37 

4.61 

1.63 

79.39 

4227 

14.03 

5.26 

1.54 

79.17 

4242 

14.28 

5.33 

1.51 

78.88 

4244 

14.49 

4.71 

1.57 

79.23 

4253 

15.01 

5.01 

1.38 

78.60 

4265 

13.98 

4.96 

1.67 

79.39 

Average  . 

14.44 

4.93 

1.56 

79.06 

Table  16  shows  the  percentages  of  protein  and  of  germ  in  both  the  low 
protein  and  high  protein  ears. 

TABLE  16. — PROTEIN  AND  GERM  IN  Low  PROTEIN  AND  HIGH  PROTEIN  CORN. 


Low  protein  corn. 


High  protein  corn. 


Ear 
No. 

Protein, 
percent. 

Germ, 
percent. 

Ear 
No. 

Protein, 
percent. 

Germ, 
percent. 

4276 

6  98 

9.52 

4174 

14.70 

13.31 

4281 

6  60 

8.81 

4189 

14  74 

9.51 

4286 

6  87 

8.42 

4202 

14  21 

11.44 

4287 

6  37 

9.53 

4212 

14.61 

10.92 

4295 

6.46 

7.95 

4218 

14.37 

11.64 

4313 

7  01 

8.98 

4227 

14  03 

11.15 

4321 

7.09 

10.30 

4242 

14.28 

13.21 

4328 

6.36 

8.88 

4244 

14.49 

11.22 

4346 

6  89 

10.14 

4253 

15  01 

9.82 

4368 

6  48 

10.79 

4265 

13.98 

12.14 

Average  .  .  . 

6  71 

9.33 

Average  .  . 

14.44 

11.44 

1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


103 


Here  again  we  see  a  slight  correlation  between  the  average  percentages 
of  protein  and  germ  in  the  corn  kernel,  although  there  are  noteworthy 
discrepancies.  Thus  we  have  an  ear  containing  6.37  percent  of  protein 
and  9.53  percent  of  germ,  while  another  ear  contains  14.74  percent  of 
protein  and  9.51  percent  of  germ.  In  other  words,  the  two  ears  contain 
practically  the  same  percentage  of  germ,  although  one  of  them  contains 
more  than  twice  as  much  protein  as  the  other.  One  of  the  lowest  pro- 
tein ears  (6.48)  contains  10.79  percent  of  germ,  while  the  highest  pro- 
tein ear  (15.01  percent)  contains  only  9.82  percent  of  germ. 

Attention  is  called  to  the  fact  that  in  selecting  seed  corn  by  chemical 
analysis  for  high  protein  there  is  a  tendency  to  increase  not  only  the  horny 
starchy  part  (which  contains  more  total  protein  than  any  other  part  of  the 
corn  kernel),  but  also  to  increase  both  the  horny  gluten  and  the  germ, 
both  of  which,  although  small  in  amount  are  rich  in  protein;  and  con- 
sequently there  is  a  slight  tendency  for  the  oil  to  be  increased,  not  only  in 
the  germ, but  also  in  the  horny  gluten  (aleurone  layer),  which  it  will  be 
remembered  is  also  quite  rich  in  oil.  This  is  the  evident  explanation  as 
to  why  there  is  a  slightly  higher  degree  of  correlation  between  oil  and 
protein  in  our  pedigreed  strains  of  corn  than  there  is  in  ordinary  corn 
which  has  not  been  so  bred. 

Tables  17  and  18  show  the  percentage  composition  of  the  low  oil  and 
high  oil  ears. 

TABLE  17. — CHEMICAL  COMPOSITION  OF  TEN  EARS  OF  "  ILLINOIS"  Low  OIL  CORN. 


Ear 
No. 

Protein, 
percent. 

Oil, 
percent. 

Ash, 
percent. 

Carbohydrates, 
percent. 

4474 

9.40 

2  68 

1.45 

86.47 

4486 

9.16 

2  65 

1.64 

86.55 

4491 

9.49 

2  60 

1.29 

86.62 

4495 

9.57 

2.59 

1.41 

86.43 

4509 

8.96 

2.53 

1.36 

87.15 

4512 

10.64 

2  45 

1.46 

85.45 

4521 

9.97 

2  12 

1.42 

86.49 

4537 

10.89 

2  40 

1.54 

85.17 

4548 

9.77 

2.54 

1.36 

86.33 

4555 

11.92 

2.65 

1.42 

84.01 

Average  . 

9.98 

2  52 

1.44 

86.07 

The  average  for  the  low  oil  corn  is  2.52  percent  of  oil  and  9.98  percent 
of  protein,  while  the  high  oil  contains  7.00  percent  of  oil  and  11.31  percent 
of  protein.  In  other  words,  the  high  oil  corn  contains  almost  three  times 
as  much  oil  as  the  low  oil  corn,  but  is  less  than  one-seventh  richer  in  pro- 
tein, showing  only  slight  correlation  between  oil  and  protein,  and  with 
several  ears  no  correlation  whatever  exists.  For  example,  we  have  one 
ear  with  10.89  percent  of  protein  and  2.40  percent  of  oil  and  another 
ear  with  10.79  percent  of  protein  and  7.01  percent  of  oil,  the  protein 


104 


BULLETIN  No.  87. 


[August, 


being  practically  equal,  while  the  one  ear  contains  nearly  three  times  as 
much  oil  as  the  other.  Again  the  low  oil  ear  No.  4555  (2.65  percent  of 
oil)  contains  11.92  percent  of  protein,  or  .61  percent  more  than  the 
average  of  all  of  the  high  oil  ears. 

TABLE  18. — CHEMICAL  COMPOSITION  OF  TEN  EARS  OP  "  ILLINOIS"  HIGH  OIL  CORN. 


Ear 

No. 

Protein, 
percent. 

Oil, 
percent. 

Ash, 
percent. 

Carbohydrates, 
percent. 

4374 

11.26 

7   10 

1.64 

80.00 

4411 

10.79 

7.01 

1.40 

80.80 

4412 

9.58 

6  87 

1.58 

81.97 

4417 

10.33 

7  01 

1.66 

81.00 

4421 

12.55 

7.02 

1.53 

78.90 

4423 

11.66 

6  95 

1.56 

79.83 

4436 

11.47 

7  17 

1.59 

79.77 

4441 

12.94 

7  37 

1.57 

78.12 

4448 

11.75 

6  78 

1.52 

79.95 

4462 

10.76 

6.74 

1.48 

81.02 

Average  . 

11.31 

7.00 

1.55 

80.14 

TABLE  19. — OIL  AND  GERM  IN  Low  OIL  AND  HIGH  OIL  CORN. 


Low  oil  corn. 

High  oil  corn. 

Ear 
No. 

Oil, 

percent. 

'  Germ, 
percent. 

Ear 
No. 

Oil, 

percent. 

Germ, 
percent. 

4474 
4486 
4491 
4495 
4509 

2.68 
2.65 
2  60 
2.59 
2.53 

8.05 
8.13 
7.92 
7.39 
7.06 

4374 
4411 
4412 
4417 
4421 

7.10 
7  01 
6  87 
7  01 
7.02 

12.90 
12.73 
13.73 
14.50 
14.65 

4512 
4521 
4537 
4548 
4555 

Average  .  . 

2.45 
2.12 
2  40 
2.54 
2.65 

7.89 
7.13 
7.57 
7.83 
8.47 

4423 
4436 
4441 
4448 
4462 

Average  .  . 

6.95 
7.17 
7  37 
6  78 
6.74 

13.83 
14.10 
14.53 

14.35 
13.03 

2  52 

7.74 

7  00 

13.84 

Table  19,  giving  the  percentages  of  oil  and  germ  in  the  low  oil  and 
high  oil  corn,  shows  a  very  marked  correlation  between  oil  and  germ. 
The  ten  low  oil  ears  contain  from  2.12  to  2.68  percent  of  oil  (average 
2.52)  and  from  7.06  to  8.47  percent  of  germ  (average  7.74),  while  the 
ten  high  oil  ears  contain  from  6.74  to  7.37  percent  of  oil  (average  7.00), 
and  from  12.73  to  14.65  percent  of  germ  (average  13.84).  There  is  no 
overlapping  and  the  correlation  is  very  distinct.  Every  low  oil  ear  con- 
tains a  small  percentage  of  germ  and  every  high  oil  ear  a  high  percentage 
of  germ.  Attention  is  called  to  the  fact  that  the  high  oil  corn  is  even 
richer  in  oil  than  would  be  indicated  by  the  high  percentage  of  germ  as 
compared  with  the  percentage  of  oil  and  germ  in  the  low  oil  corn,  indicat- 
ing that  the  breeding  for  high  oil  has  not  only  increased  the  oil  by  in- 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


105 


creasing  the  percentage  of  germ  (which  contains  most  of  the  oil),  but  that 
the  percentage  of  oil  in  the  germ  itself  has  increased.  (Of  course  there 
is  also  an  increase  in  the  percentage  of  oil  in  the  horny  glutenous  part.) 
Similarly  the  percentage  of  oil  has  decreased  even  more  rapidly  than  the 
percentage  of  germ  in  the  low  oil  corn.  These  results  are  very  apparent 
in  the  data  shown  in  Table  20. 

EFFECT  OF  BREEDING  ON  COMPOSITION  OF  GERMS  AND  ENDOSPERMS. 
As  already  explained,  ten  ears  were  selected  from  each  of  the  four 
different  strains  of  corn  (low  protein,  high  protein,  low  oil,  and  high  oil), 
and  twenty-five  kernels  were  taken  from  each  of  these  forty  ears,  the 
germ  being  separated  from  the  remainder  of  the  kernel,  which  we  call 
the  endosperm.  After  the  percentage  of  germ  was  determined  from  each 
individual  ear,  the  germs  from  each  lot  of  ten  ears  were  put  together  to 
make  two  samples,  each  sample  representing  five  ears.  The  endosperms 
were  likewise  put  together,  so  that  we  have  duplicate  samples  of  both 
germs  and  endosperms  for  each  of  the  four  different  strains.  These 
samples  were  analyzed  chemically  and  the  results  are  given  in  Table  20. 

TABLE  20. — CHEMICAL  COMPOSITION  OF  GERMS  AND  ENDOSPERMS  FROM  Low  PRO- 
TEIN AND  HIGH  PROTEIN  CORN  AND  FROM  Low  OIL 
AND  HIGH  OIL  CORN. 


Kind  of 
corn. 

Part  of 
kernel. 

Protein, 
percent. 

Oil, 

percent. 

Ash, 
percent. 

Carbo- 
hydrates, 
percent. 

Low  protein  

Germs 

(  18.05 
I  17.96 

33.59 
34.60 

10.19 
10.16 

38.17 
37.28 

High  protein  .... 
Low  oil  

Germs 
Germs 

\  20.85 
121.65 

$21.70 

34.99 
36.02 

25.01 

10.12 
10.07 

13.13 

34.04 
32.26 

40.16 

High  oil  

Germs 

(21.71 
(  17.55 

24.62 
41.76 

13.36 

8.75 

40.31 
31.94 

I  17.84 

41.75 

8.81 

31.60 

Low  protein  

Endosperms 

\    5.69 
(    5.68 

.83 
.91 

.43 
.43 

93.05 
92.98 

High  protein  .... 
Low  oil  . 

Endosperms 
Endosperms 

(  13.67 
1  13.92 

{    9  13 

.76 
.72 

52 

.36 
.41 

.47 

85.21 
84.95 

89.88 

High  oil  

Endosperms 

\    9.14 
(  10.62 

.51 
1.07 

.43 
.36 

89.92 

87.95 

1  10.10 

1.24 

.39 

88.27 

These  results  show  in  a  very  striking  manner  the  effect  of  breeding  in 
changing  the  composition  of  the  different  physical  parts  of  the  kernel. 
Thus  the  germs  from  the  low  oil  corn  contain  about  25  percent  of  oil, 
while  those  from  the  high  oil  corn  contain  nearly  42  percent  of  oil.  As 


106  BULLETIN  No.  87.  [August, 

stated  above,  breeding  to  change  the  oil  content  not  only  changes  the 
percentage  of  germ,  but  it  also  changes  the  percentage  of  oil  in  the  germ. 
It  should  also  be  noted  that  endosperms  from  the  high  oil  corn  contain 
more  than  twice  as  much  oil  as  those  from  the  low  oil  corn,  although  the 
percentage  of  oil  in  the  endosperm  is  very  small  even  in  the  high  oil  corn, 
and  this  oil  is  largely  contained  in  the  horny  gluten. 

Perhaps  the  most  marked  and  valuable  results  are  shown  in  the  per- 
centages of  protein  contained  in  the  endosperms  from  low  protein  and 
high  protein  corn;  the  endosperms  from  the  low  protein  corn  contain  less 
than  6  percent  of  protein,  while  those  from  the  high  protein  corn  con- 
tain nearly  14  percent  of  protein.  These  results,  in  connection  with 
others  which  we  have  given,  would  seem  to  prove  very  conclusively 
that  to  select  high  protein  seed  corn  by  mechanical  examination  we  should 
select  principally  for  a  large  proportion  of  the  more  nitrogenous  part  of 
the  endosperm;  that  is,  the  horny  part.  To  select  only  for  large  germs 
will  have  only  a  slight  effect  upon  the  protein  content  of  the  corn,  al- 
though it  will  produce  a  rapid  and  marked  increase  in  the  oil  content. 

Referring  again  to  Table  20,  it  will  be  seen  that  the  endosperms  from 
the  high  oil  corn  contain  about  one  percent  more  protein  than  those  from 
the  low  oil  corn.  On  the  other  hand,  the  germs  from  high  oil  corn  con- 
tain less  protein  (17.7  percent)  than  those  from  low  oil  corn  (21.7  per- 
cent), the  difference  being  4  percent  protein  in  favor  of  the  low  oil  corn. 

These  results  were  to  be  expected  even  from  a  study  of  the  analyses  of 
the  163  ears  reported  in  Bulletin  No.  55,  in  1899,  which  showed  that  large 
germs  were  naturally  even  richer  in  oil  than  the  size  of  the  germs  would 
indicate,  and  that  there  is  but  very  slight  correlation  between  oil  and  pro- 
tein, the  increased  oil  tending  to  decrease  the  percentage,  though  not  the 
actual  amount  of  protein  in  the  germ.  It  will  be  seen  from  Tables  19  and 
20  that  the  high  oil  corn  contains  nearly  twice  as  much  germ  as  the  low 
oil  corn,  and  that  the  germs  from  high  oil  corn  are  more  than  one  and  one- 
half  times  richer  in  oil  than  the  germs  from  the  low  oil  corn;  but  that, 
although  the  high  oil  germs  contain  a  larger  total  amount  of  protein 
because  of  their  increased  size),  they  are  really  considerably  poorer  in 
percentage  of  protein  than  the  low  oil  germs. 

It  is  perhaps  worth  while  to  consider  the  evident  fact  that,  even  if  the 
protein  should  increase  in  the  germ  in  the  same  proportion  as  the  oil 
(which  is  not  the  case),  we  should  need  to  increase  the  oil  two  pounds  for 
every  one  pound  increase  in  protein  obtained,  if  we  depend  upon  the 
method  of  picking  our  high  protein  seed  corn  by  selecting  for  large  germs. 
In  other  words,  to  increase  the  protein  in  corn  from  10  percent  to  15  per- 
cent by  this  method,  would  require  the  oil  in  the  corn  to  be  increased 
from  5  percent  to  15  percent. 

Although  we  do  not  assume  to  say  what  should  be  the  percentage  of 
oil  in  corn  for  feeding  purposes,  we  do  take  the  liberty  of  raising  the  ques- 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


107 


tion  whether  the  popular  opinion  that  the  oil  in  corn  should  be  increased 
for  feeding  purposes  may  not  be  erroneous.  Certainly  the  investigations 
of  Lehmann  in  Germany  and  of  Shutt  in  Canada  have  indicated  very 
strongly  that  corn  is  already  too  rich  in  oil  to  be  suitable  as  a  foodstuff 
for  bacon  hogs.  It  may  also  be  called  to  mind  that  some  other  excellent 
foodstuffs,  such  as  oats,  bran,  barley,  red  clover  and  alfalfa,  contain  less 
than  half  as  much  oil  as  is  already  contained  in  ordinary  corn. 
•  Attention  is  called  to  the  fact  that  although  the  physical  parts  of  the 
corn  kernel  which  contain  nearly  all  of  the  oil  (namely  the  germ  and  the 
horny  gluten)  also  contain  most  of  the  ash,  yet  a  high  percentage  of  ash 
in  the  germs  is  associated  with  a  low  percentage  of  oil,  and  vice  versa, 
indicating  that  the  ash  content  of  the  germ  (which  includes  the  major 
part  of  the  ash  of  the  entire  kernel)  bears  a  more  constant  relation  to  the 
oil-free  material  in  the  germ  than  to  the  whole  germ.  By  computation 
we  find  that  the  oil-free  germs  contain  the  percentages  of  ash  given  in 
Table  21  (assuming  the  oil  to  contain  no  ash,  which  is  approximately 
correct*). 

TABLE  21. — PERCENTAGE  OF  ASH  IN  GERMS. 


In  fresh 
germs. 

In  oil-free 
germs. 

From  low  protein  corn  .                               .                 

U0.19 

15.34 

From  high  protein  corn  

\  10.16 
(  10.12 

15.54 
15.57 

From  low  oil  corn  . 

{  10.07 
(  13.13 

15.74 
17.51 

From  high  oil  corn     

I  13.36 
(    8.75 

17.72 
15.02 

{    8.81 

15.12 

Breeding  for  high  or  low  protein  produces  no  marked  effect  upon  the 
ash  content  or  the  oil  content  of  either  the  germs  or  the  endosperms,  and 
only  slightly  influences  the  protein  content  of  the  germs.  (The  low  pro- 
tein germs  contain  about  18  percent  of  protein  and  the  high  protein 
germs  about  21  percent.)  The  results  show  that  such  breeding  produces 
exceedingly  marked  effects  upon  the  protein  content  of  the  endosperms, 
the  low  protein  endosperms  containing  less  than  6  percent  and  the  high 
protein  endosperms  nearly  14  percent  of  protein.  In  this  connection  it 
is  well  to  remember  that  the  corn  kernel  usually  contains  only  about  11 
percent  of  germ,  while  the  endosperm  amounts  to  about  89  percent  of  the 
kernel.  The  significance  of  this  becomes  more  readily  apparent  by  an 
examination  of  Table  22,  which  shows  where  the  protein  actually  exists 
in  100  pounds  of  corn. 


*Actual  determinations  of  the  ash  in  corn  oil  have  shown  that  the  oil  contains 
only  0.2  per  cent  of  ash. 


108 


BULLETIN  No.  87. 


[August, 


TABLE  22. — PROTEIN  IN  100  POUNDS  OF  CORN. 


Names 
of 
parts. 

Low  protein  corn. 

High  protein  corn. 

Differ- 
ence. 

Percent 
of 
corn. 

Percent 
of 
protein. 

Pounds 
of 
protein. 

Percent 
of 
corn. 

Percent 
of 
protein. 

Pounds 
of 
protein. 

Pounds 
of 
protein. 

In  germs  . 

9.33 
90.67 

18.01 
5.69 

1.68 
5.16 

11.44 
88.56 

21.25 
13.80 

2.43 
12  22 

.75 

7.06 

In  endosperms 

We  thus  find  as  a  result  of  corn  breeding  that  in  the  seventh  genera- 
tion we  have  a  maximum  difference  of  only  .75  pound  of  protein  in  the 
germs  from  100  pounds  of  low  protein  and  high  protein  corn,  while  in  the 
endosperms  from  these  two  kinds  of  corn  we  have  a  difference  of  7.06 
pounds  of  protein,  in  100  pounds  of  corn.  In  other  words,  in  changing 
the  protein  content  of  corn  the  effect  produced  in  the  endosperms  amounts 
to  almost  ten  times  the  effect  produced  in  the  germs. 

THE  COMPOSITION  OF  HOMINY  MILL  PRODUCTS. 

Besides  the  investigations  which  we  have  carried  on  along  this  particu- 
lar line  in  connection  with  our  work  of  corn  breeding,  we  have  also  made 
some  study  of  factory  products,  especially  the  products  from  hominy 
mills,  which  make  use  of  immense  quantities  of  corn. 

In  the  regular  process  of  milling  corn,  a  very  large  number  of  separa- 
tions are  made  and  several  distinctly  different  final  products  are  obtained, 
some  of  which  are  composed  almost  entirely  of  certain  distinct  physical 
parts  of  the  corn  kernel.  The  following  is  a  brief  and  very  general  de- 
scription of  the  usual  process  of  corn  milling : 

The  whole  corn  is  somewhat  softened  by  steaming  and  is  then  run 
through  a  hulling  machine,  which  not  only  removes  the  hull,  but  loosens 
the  germ  and  breaks  off  the  horny  gluten  and  more  or  less  white  starch. 
The  dust  or  pulverized  material  coming  from  the  hulling  machine  con- 
sists largely  of  white  starch  and  horny  gluten.  The  hulls  and  germs  are 
each  separated  but  not  in  very  pure  condition,  leaving  what  is  termed 
hominy,  which  consists  chiefly  of  the  horny  starchy  part  of  the  kernel, 
with  more  or  less  adhering  white  starch. 

The  product  which  is  known  as  grits  is  made  from  the  hominy  and 
consists  of  the  horny  starchy  part  separated  in  very  pure  form.  In 
making  grits  the  coarse  hominy  is  run  through  a  grinding  machine  and 
reduced  to  a  coarse  powder  which  may  be  termed  coarse  grits,  much  of 
the  adhering  white  starch  being  rubbed  off  from  the  horny  starch  in  this 
process.  The  coarse  grits  are  then  run  through  one  or  two  more  grinding 
machines,  until  the  horny  starch  is  reduced  to  a  rather  fine  powder,  which 
may  be  termed  fine  grits.  This  material  consists  of  the  horny  starch  in 
very  pure  condition.  After  each  grinding  the  fine  dust  consisting  largely 


1903.] 


THE  STRUCTURE  OF  THE  CORN  KERNEL. 


109 


of  the  white  starch  is  separated  from  the  grits  and  goes  into  the  product 
known  as  corn  flour. 

.  In  addition  to  the  corn  flour  thus  regularly  separated  and  handled  in 
considerable  quantities,  there  is  constantly  produced  a  small  amount  of 
what  is  termed  "  break"  flour.  This  is  an  exceedingly  fine  dust  also  pro- 
duced in  the  process  of  breaking  the  corn  particles  in  the  grinding  machines 
which  reduce  the  hominy  to  grits.  The  break  flour  is  carried  from  the 
machine  by  an  air  current  through  conduits  and  finally  collected.  This 
is  another  very  pure  form  of  the  white  starch. 

Thus,  in  the  regular  milling  process  there  are  two  physical  parts  of  the 
corn  kernel  separated  in  very  pure  form:  namely,  horny  starch  (fine 
grits)  and  white  starch  (break  flour  or  corn  flour)  and  two  other  distinct 
parts  which  are  separated  somewhat  less  perfectly,  the  hulls  and  the 
germs. 

By  the  courtesy  of  the  manager  of  the  American  Hominy  Company's 
Mills  at  Decatur  we  were  allowed  to  collect  representative  samples  of 
these  different  products  for  analysis.  The  composition  of  these  products 
is  given  in  Table  23,  and  it  will  be  found  interesting  to  compare  these 
results  with  the  composition  of  the  same  products,  or  parts,  which  were 
obtained  by  exact  hand  separation,  as  given  in  Table  1.  For  conve- 
nience in  comparison  Table  23  also  shows  the  composition  of  these  parts 
as  obtained  from  Ear  No.  1  (Table  1),  which  is  very  similar  to  the  corn 
which  was  being  used  in  the  mill  at  the  time  the  samples  were  taken. 
This  was  fairly  representative  of  the  ordinary  white  corn  grown  in  1902, 
nearly  all  of  which  was  abnormally  low  in  protein,  owing  to  seasonal  in- 
fluences. 

TABLE  23. — COMPOSITION  OF  PARTS  OP  THE  CORN  KERNEL  SEPARATED  BY 
HOMINY  MILL  AND  BY  HAND. 


Names  of  parts. 

Methods  of 
separation. 

Protein, 
percent. 

Oil, 

percent. 

Ash, 
percent. 

Carbo- 
hydrates, 
percent. 

Hulls  .. 

By  mill 

6  85 

2.94 

1.11 

89.10 

Hulls  

By  hand 

4  97 

.92 

.82 

93.29 

Horny  starch  (fine  grits)  .  . 
Horny  starch  

By  mill 
By  hand 

8.46 
8.12 

.44 
.16 

.26 
.18 

90.84 
91.54 

White  starch  (corn  flour*)  . 
White  starch  (break  flour) 
White  starch  (from  tip)  .  .  . 

Germs  

By  mill 
By  mill 
By  hand 

By  mill 

5.91 
5.88 
6.10 

15.84 

1.63 
2.04 
.29 

21.26 

.49 
.68 
.29 

7.41 

91.97 
91.40 
93.31 

55.49 

By  hand 

19  91 

36  54 

10  48 

33  07 

Whole  corn  

Mill  sample 

9  31 

4  20 

1.43 

85.06 

Whole  corn  

Ear  No.  1 

9.28 

4.20 

1.41 

85.11 

*Obtained  by  direct  separation  from  grits. 


110  BULLETIN  No.  87.  [August, 

In  general  the  composition  of  these  mill  separations  agrees  with  the 
composition  of  the  same  parts  separated  by  hand,  although  in  nearly 
all  cases  the  mill  products  show  more  or  less  contamination  or  mixture 
with  other  parts  of  the  kernel.  Thus  the  mill  hulls  are  noticeably  high 
in  protein  and  oil  owing  to  the  presence  of  some  particles  of  horny  gluten 
and  germ;  while  the  mill  germs  are  too  low  in  protein  and  oil  because  of 
the  presence  of  some  hulls  and  tip  caps.  Furthermore,  some  oil  is  lost 
from  the  germ  and  absorbed  by  other  parts  in  the  milling  process. 
The  fine  grits  are  almost  pure  horny  starch,  except  that  they  contain 
about  twice  as  much  oil  as  the  hand-separated  product.  This  is  doubt- 
less due  to  the  fact  that  some  germs  are  broken  or  crushed  in  the  hulling 
machine  and  the  liberated  oil  is  absorbed  to  some  extent  by  the  hominy, 
chiefly,  of  course,  by  the  white  starch,  as  indicated  by  the  high  oil  content 
of  the  break  flour  and  the  other  regularly  separated  corn  flour,  although 
it  is  evident  that  a  small  portion  of  this  liberated  oil  remains  adhering  to 
the  fine  grits.  The  white  starch  contains  5.88  to  5.91  percent  of  protein, 
while  the  horny  starch  (fine  grits)  contains  8.46  percent,  or  almost  one- 
half  more. 

It  will  be  observed  that  the  two  samples  of  whole  corn  are  almost 
identical  in  composition.  While  the  corn  is  fairly  representative  of 
much  of  the  white  corn  grown  during  the  season  of  1902,  attention  is 
called  to  the  apparent  fact  that  this  is  not  the  most  suitable  corn  for  the 
manufacture  of  hominy  and  grits.  It  seems  evident  that  corn  containing 
a  higher  percentage  of  the  horny  starchy  part  would  be  more  valuable  for 
the  hominy  mill.  The  manager  of  the  American  Hominy  Company's 
Mills  at  Decatur  has  assured  the  writer  that  he  prefers  corn  which  shall 
run  high  in  grits  (horny  starch),  but  he  does  not  desire  that  the  oil  content 
should  be  increased;  indeed,  it  would  be  much  better  for  milling  purposes 
to  have  the  percentage  of  oil  in  corn  reduced,  because  of  the  difficulty  of 
preventing  the  oil  from  being  absorbed  by  other  products  and  injuring 
their  quality,  the  tendency  being  for  the  oil  to  become  rancid  when  ex- 
posed to  the  air.  The  hominy  mills  offer  some  encouragement  to  farmers 
to  grow  corn  especially  suited  to  their  use. 

SUMMARY  OF  BULLETIN  No.  87. 

The  investigations  reported  in  this  bulletin  serve  to  establish  the  fol- 
lowing facts: 

1.  The  kernel  of  corn  consists  of  six  readily  observable  and  distinctly 
different  physical  parts,  which  are  known  as  (1)  the  tip  cap,  (2)  the  hull 
(3)  the  horny  gluten,  (4)  the  horny  starch,  (5)  the  white  starch,  (6)  the 
germ. 

2.  The  tip  cap  covers  the  tip  or  base  of  the  kernel  and  comprises  only 
about  1.5  percent  of  the  grain. 

3.  The  hull  is  the  very  thin  outer  coat.    It  comprises  about  6  percent 


190:5.]  THE  STRUCTURE  OK  THE  CORN  KEHNEL.  Ill 

of  the  kernel  and  contains  a  lower  percentage  of  protein  (about  4  percent) 
than  any  other  part  of  the  kernel. 

4.  The  horny  glutenous  part  (aleurone  layer)  lies  underneath  the  hull 
surrounding  the  kernel.    It  comprises  from  8  to  14  percent  of  the  grain 
(being  more  abundant  in  high  protein  corn),  and  it  contains  from  20  to 
25  percent  of  protein,  being  the  richest  in  protein  of  all  the  parts  of  the 
corn  kernel. 

5.  The  horny  starchy  part  is  the  chief  substance  in  the  sides  and  back 
of  the  kernel  (the  germ  face  being  considered  the  front  of  the  kernel). 
This  substance  comprises  about  45  percent  of  ordinary  corn,  but  is  much 
more  abundant  in  high  protein  corn  and  less  abundant  in  low  protein. 
Although  rich  in  starch  it  contains  about  10  percent  of  protein  (more  in 
the  high  protein  corn  and  less  in  low  protein  corn).     It  contains  a  greater 
total  amount  of  protein  than  any  other  part  of  the  kernel. 

6.  The  white  starchy  part  occupies  the  center  of  the  crown  end  of  the 
kernel  and  usually  partially  surrounds  the  germ.     It  comprises  about  25 
percent  of  the  kernel  (less  in  high  protein  corn  and  more  in  low  protein 
corn).     It  is  poor  in  protein  (5  to  8  percent). 

7.  The  germ  occupies  the  central  part  of  the  kernel  toward  the  tip 
end.   It  comprises  about  11  per  cent  of  the  kernel  (more  in  high  oil  corn 
and  less  in  low  oil  corn).    The  germ  contains  from  35  to  40  percent  of 
corn  oil  or  from  80  to  85  percent  of  the  total  oil  content  of  the  corn  kernel. 

8.  High  protein  corn  contains  a  large  proportion  of  the  horny  parts 
(both  of  the  horny  glutenous  part  and  the  horny  starchy  part),  and  a 
correspondingly  smaller  proportion  of  the  white  starchy  part.     The  horny 
parts  comprise  more  than  60  percent  of  high  protein  corn  and  contain 
about  80  percent  of  the  total  protein  content  of  very  high  protein  corn. 

9.  The  value  and  reliability  of  the  method  proposed  in  previous 
bulletins  by  which  any  farmer  can  select  high  protein  seed  corn  (selecting 
for  a  large  proportion  of  horny  parts)  by  a  simple  mechanical  examina- 
tion of  the  corn  kernels  has  been  fully  confirmed  by  the  results  which 
have  been  subsequently  obtained  and  which  are  now  reported  in  this 
bulletin. 

10.  The  value  of  the  method  proposed  for  picking  out  high  oil  seed 
corn  by  selecting  for  a  large  proportion  of  germ  is  also  fully  established. 

11.  The  degree  of  correlation  existing  in  the  corn  kernel  between  the 
percentages  of  germ  and  protein  is  very  slight  and  is  frequently  entirely 
absent,  consequently  the  proportion  of  germ  in  the  corn  kernel  is  not  a 
reliable  index  of  its  protein  content. 

12.  The  composition  of  the  different  products  obtained  from  corn  by 
hominy  mills,  as  well  as  by  other  factories,  serves  greatly  to  emphasize 
the  importance  of  breeding  corn  for  special  purposes. 

(For  more  complete  details  of  corn  breeding,  the  reader  is  referred  to 
Bulletin  .No-  82.  "  Methods  of  Corn  Breeding,"  which  can  be  obtained  upon 


112  BULLETIN  No.  87.  [August,  1903. 

request  from  the  Illinois  Experiment  Station,  Urbana,  Illinois.  The 
supply  of  Bulletin  No.  53  and  Bulletin  No.  55,  both  relating  to  corn 
investigations,  is  now  exhausted.) 


UNIVERSITY  OF  ILLINOIS-URBANA 


